The present invention relates to a device for counterbalancing a swivelable body part on a motor vehicle, especially a trunk lid on an automobile, with a hinge for the swivelable body part or lid and a torsion bar, said bar being bent to form a crank in the vicinity of a movable hinge part of the hinge, an intermediate lever being articulated to the hinge part and engaging the crank, the crank including a crank pin between two legs, the legs being connected by arcuate sections with both the crank pin and the torsion rod.
A device of this kind is known, for example, from German Auslegeschrift No. 1,003,059. In this known design, the crank in the torsion rod, is made U-shaped, with legs parallel to one another. The arcuate sections at the transitions from the torsion rod to the legs, and from the legs to the crank pin, are made with a relatively small radius of curvature. In this manner, with a short mutual spacing of the legs, a crank pin, said pin being straight in its central area, is produced for reliable mounting of the intermediate lever. Also, in this design, the bearings, required on both sides of the crank to support the torsion rod, can be disposed with a small mutual spacing between them. This produces a device which requires only a small amount of space for installation in the trunk.
However, the small radii of curvature in the torsion rod in the vicinity of the crank in this known device is particularly disadvantageous in that it results in a considerable amount of waste and, consequently increased cost for the manufacture of the crank in the torsion rods, especially when reducing the weight of torsion rods made from expensive materials.
Therefore, an object of the present invention is to provide a device of the aforementioned type wherein the crank in the torsion rod is such that minimum waste results, with ease of manufacture and small installation space requirements for the crank.
This object is attained according to the present invention by providing that the legs of the crank are made S-shaped.
In the device according to the present invention narrow bending radii are avoided with conventional spacings of the crank pin from the torsion bar. Further, according to the present invention, the arcuate segments of the S-shaped legs, which terminate in the torsion bar, can be brought close together to provide a narrow crank and hence one which requires little room for installation. Such an arrangement also permits the support bearings for the torsion bar, usually provided on either side of the crank, to be located a short distance apart whereby narrow and consequently light bearing arrangements, for example on a bearing plate, can be employed.
With an appropriate choice of curve radii for the arcuate segments of the S-shaped legs connected with the crank pin, it is possible according to the present invention to provide a crank pin which is straight in its middle area for reliable support of the intermediate lever.
Further, it has been found to be advantageous in the device of the present invention, where the torsion bar is made from round stock, to provide that the average bending radius of each arcuate segment of the legs is equivalent a diameter at least twice the diameter of the torsion bar.
According to the present invention, the arcuate segments of each leg can merge directly with each other. According to another feature, the legs can have a straight intermediate segment between their arcuate segments, whereby the intermediate segments meet at an acute angle. Cranks of this type, with intermediate segments in the S-shaped legs converging in the direction of the torsion bar, are advantageous from the manufacturing standpoint for maintenance of accurate dimensions and shape. This design is especially advantageous for larger distances between the crank pin and the torsion bar axis, whereby the crank is given a trapezoidal shape by long intermediate sections.